원문정보
초록
영어
The role of periplasmic oxidative defense proteins, copper, zinc superoxide dismutase (SodC) and thiol peroxidase (Tpx), of the Shiga Toxin-producing Escherichia coli O157:H7 (STEC) in biofilm formation was investigated. Proteomic analyses have shown that expression of both periplasmic antioxidant systems (SodC and Tpx) were significantly increased in STEC cells grown under biofilm conditions when compared to planktonic cells. Analysis of their growth phase-dependent gene expression indicated that a high level of the sodC expression occurred during the stationary phase and that the expression of the tpx gene is highly induced only during the exponential growth phase. The aerobic growth of STEC sodC and tpx mutants were reduced more than that of their parental strain by exogenous hydrogen peroxide. The two mutants also displayed significant reductions in attachment to both biotic (HT-29 epithelial cell) and abiotic surfaces (polystyrene and polyvinyl chloride microplates) during static aerobic growth although the growth rates of both wild type and mutants are similar during aerobic growth conditions. The STEC biofilm formation was only observed with wild type STEC cells in glass capillary tubes under continuous flow-culture system conditions compared to the STEC sodC and tpx mutants. The data presented here suggest that biofilms are physiologically heterogeneous and that oxidative stress defenses from both exponential and stationary growth stages play important roles in STEC biofilm formation. Further analysis of the role of DsbA (disulfide bond forming periplasmic enzyme) in E. coli O157:H7 on attachment, biofilm formation and virulence will be discussed.